Operators on weights

`+` [add](weight.add.ipynb) Sum
`*` [multiply](weight.multiply.ipynb) Product
`**` [multiply](weight.multiply.ipynb) Repeated multiplication
`&` [conjunction](weight.conjunction.ipynb) Conjunction
`/` [ldivide](weight.ldivide.ipynb) Left quotient
`//` [rdivide](weight.rdivide.ipynb) Right quotient